190 ◾ Fundamental Food Microbiology
The characteristic flavor of sauerkraut is the result of the combined effects of lactate, acetate,
ethanol, CO 2 , and diacetyl in proper amounts.
Genetics
If starters are developed in the future for controlled fermentation, some of the characteristics that
will be important are rapid acid production, good flavor production, low CO 2 production (to
reduce any gassy defect), and the ability to produce antimicrobial compounds, especially against
pathogens.
Microbial Problems
Off-flavor, a soft texture, and discoloration of sauerkraut can occur because of the growth of molds
and yeasts when air is not completely excluded. A slimy texture of sauerkraut can occur as a result
of the overgrowth of Leuconostoc spp. in the presence of sucrose; they metabolize fructose but synthesize dextrans from glucose (also see Chapter 20).
Conclusion
Food fermentation involves the use of specific starter cultures in different types of foods as starting
materials. The starting materials can be milk, meat, fish, fruits, vegetables, grains, seeds, and others. They are used separately or in combination. The current trend is to use controlled fermentation
in place of natural fermentation. Improvement of strains has helped overcome some of the drawbacks of controlled fermentation. Information on genomes will help improve strains in the future.
QUESTIONS
1. Define and discuss the advantages of different methods used to produce fermented foods.
2. Briefly discuss the factors to be considered while selecting milk to produce fermented dairy
products.
3. List the characteristics of buttermilk and describe how they help select specific starter
cultures.
4. Describe the symbiotic growth of starter cultures used in the production of yogurt. What
genetic improvement will be important in these strains?
5. Most commercial yogurt now contains Lab. acidophilus and Bifidobacterium with regular
yogurt bacteria. However, they are added to yogurt after fermentation. Briefly discuss the
reasons.
6. In creamed cottage cheese, cream ripened with diacetyl-producing lactic starter is often used
instead of using this starter during fermentation. Discuss the reasons.
7. Discuss the biochemical basis of the typical flavor of Cheddar cheese. What is the basis of
bitter flavor formation? How can it be reduced by genetic improvement of the starters?
8. Discuss the role of starter cultures in the development of desired characteristics in Swiss
cheese.
9. Describe the role of molds in blue cheese production. What precautions should be taken in
selecting the mold strains?
10. Discuss the methods used to accelerate cheese ripening.
The characteristic flavor of sauerkraut is the result of the combined effects of lactate, acetate,
ethanol, CO 2 , and diacetyl in proper amounts.
Genetics
If starters are developed in the future for controlled fermentation, some of the characteristics that
will be important are rapid acid production, good flavor production, low CO 2 production (to
reduce any gassy defect), and the ability to produce antimicrobial compounds, especially against
pathogens.
Microbial Problems
Off-flavor, a soft texture, and discoloration of sauerkraut can occur because of the growth of molds
and yeasts when air is not completely excluded. A slimy texture of sauerkraut can occur as a result
of the overgrowth of Leuconostoc spp. in the presence of sucrose; they metabolize fructose but synthesize dextrans from glucose (also see Chapter 20).
Conclusion
Food fermentation involves the use of specific starter cultures in different types of foods as starting
materials. The starting materials can be milk, meat, fish, fruits, vegetables, grains, seeds, and others. They are used separately or in combination. The current trend is to use controlled fermentation
in place of natural fermentation. Improvement of strains has helped overcome some of the drawbacks of controlled fermentation. Information on genomes will help improve strains in the future.
QUESTIONS
1. Define and discuss the advantages of different methods used to produce fermented foods.
2. Briefly discuss the factors to be considered while selecting milk to produce fermented dairy
products.
3. List the characteristics of buttermilk and describe how they help select specific starter
cultures.
4. Describe the symbiotic growth of starter cultures used in the production of yogurt. What
genetic improvement will be important in these strains?
5. Most commercial yogurt now contains Lab. acidophilus and Bifidobacterium with regular
yogurt bacteria. However, they are added to yogurt after fermentation. Briefly discuss the
reasons.
6. In creamed cottage cheese, cream ripened with diacetyl-producing lactic starter is often used
instead of using this starter during fermentation. Discuss the reasons.
7. Discuss the biochemical basis of the typical flavor of Cheddar cheese. What is the basis of
bitter flavor formation? How can it be reduced by genetic improvement of the starters?
8. Discuss the role of starter cultures in the development of desired characteristics in Swiss
cheese.
9. Describe the role of molds in blue cheese production. What precautions should be taken in
selecting the mold strains?
10. Discuss the methods used to accelerate cheese ripening.